Jan. 9, 2006
Erica Hupp
Headquarters, Washington
(202) 358-1237
Donna Weaver
Space Telescope Science Institute, Baltimore
(410) 338-4493
David Aguilar
Harvard-Smithsonian Center for Astrophysics, Cambridge, Mass.
(617) 495-7462
RELEASE: 06-004
THERE'S MORE TO THE NORTH STAR THAN MEETS THE EYE
By stretching the capabilities of NASA's Hubble Space Telescope to the
limit, astronomers photographed the close companion to Polaris, known
also as the North Star, for the first time.
"Hubble's exceptional pointing capabilities combined with the
wonderful performance of its instruments allow scientists to see the
universe in finer detail than ever before," said Michael Moore,
NASA's Hubble program executive. "It is that clear vision that makes
these types of images possible," he added.
The North Star is thought to be a steady, solitary point of light that
guided sailors for ages, but there is more to this star than meets
the eye. The North Star is actually a triple star system. While one
companion is easily viewed with small telescopes, the other hugs
Polaris so tightly that it has never been seen until now.
"The star we observed is so close to Polaris that we needed every
available bit of Hubble's resolution to see it," said astronomer
Nancy Evans of the Harvard-Smithsonian Center for Astrophysics,
Cambridge, Mass. The companion proved to be less than two-tenths of
an arcsecond from Polaris. That is an incredibly tiny angle
equivalent to the apparent diameter of a quarter located 19 miles
away. At the system's distance of 430 light-years from Earth, that
translates into a separation of about 2 billion miles.
"The brightness difference between the two stars made it even more
difficult to resolve them," said astronomer Howard Bond of the Space
Telescope Science Institute, Baltimore. Polaris is a super-giant more
than two thousand times brighter than the sun, while its companion is
a dwarf star. "With Hubble, we've pulled the North Star's companion
out of the shadows and into the spotlight," he said.
"Our ultimate goal is to get the accurate mass for Polaris," Evans
said. "To do that, the next milestone is to measure the motion of the
companion in its orbit," she added. Astronomers want to determine the
mass of Polaris, because it is the nearest Cepheid variable star.
Cepheids' brightness variations are used to measure the distances of
galaxies and the expansion rate of the universe. It is essential to
understand their intrinsic physics makeup and evolution. Knowing
their mass is the most important ingredient in this understanding.
The researchers plan to continue observing the Polaris system for
several years. The movement of the small companion during its 30-year
orbit around the primary should be detectable. The researchers
presented their data today during the 207th meeting of the American
Astronomical Society in Washington.
The Hubble Space Telescope is a project of international cooperation
between NASA and the European Space Agency. The Space Telescope
Science Institute in Baltimore conducts Hubble science operations.
The Institute is operated for NASA by the Association of Universities
for Research in Astronomy, Inc., Washington.
For images and additional information about this research on the Web,
visit:
http://hubblesite.org/news/2006/02
For information about NASA and agency programs on the Web, visit:
http://www.nasa.gov/home
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